The anterior cruciate ligament (ACL) is one of the four important ligaments that stabilize the knee joint. Ligaments are made of inelastic tough fibrous material that serve to control and limit movement of a joint. The ACL is the primary restraint to forward motion of the shin bone (tibia) on the thigh bone (femur). In addition the ACL controls knee extension and inward rotation of the shin bone on the thigh bone. The ACL functions by attaching to the front top of the tibia and to the back bottom of the femur bone.

How It Happens

ACL injuries happen in various conditions. Most common ACL injuries occur during sporting activities such as football, soccer, skiing or snowboarding. Other mechanisms that can cause an ACL tear include severe trauma such as in a motor vehicle accident and work injuries in which the shin bone rotates outward or the thigh bone is forced backward with the knee fully bent.

Symptoms

Sudden onset of pain, along with a feeling of the joint ‘giving out’ or buckling and some may hear
a popping sound.

An initial sign of an ACL tear is swelling of the joint.

If the injury is an isolated ACL tear (relatively rare) the pain may be felt in a more generalized discomfort throughout the knee joint.

Pain is often continuous, deep and fairly localized. It increases with any movement that stresses the ligament (such as over-extending the knee while weight is on it).

Tendency to hobble when walking and keep the knee slightly bent.

Testing

MRI and arthrograms are used to view tears of the ACL.

What Causes It?

The ACL is most commonly injured during sporting activities when a person suddenly pivots causing excessive rotational forces on the ligament. Other mechanisms that can cause an ACL tear include a blow against the top of the thigh while the knee is close to full extension, the knee forced into hypertension or a blow behind the knee forcing the tibia forward. One of the most common mechanisms occurs when a football player is tackled from the side with the foot planted and the knee slightly bent as the player tries to “cut away.” In this case, not only does the ACL tear but also the medial meniscus and the medial collateral ligament (MCL) resulting an the injury commonly known as the “unhappy triad.”

What Should You Do?

Following an ACL injury the primary goal is to reduce the swelling and inflammation and provide relief for the pain. This is done by placing an ice pack on the knee for 10 minutes at a time, several times a day. The knee should be moved only within the within the pain free range to allow the healing process to proceed without further damaging the ACL. Twisting and full bending of the knee should be avoided.

Will Physiotherapy Help Me?

Some ACL injuries may require surgical intervention, and others may not. In both cases, physiotherapy can offer helpful ways to enhance the healing process of the ACL.

Initially the physiotherapist will place an emphasis on the control of swelling, inflammation and pain. As the healing process progresses the physiotherapist will concentrate on the flexibility and strength of the joint.

The physiotherapist will offer appropriate exercise sequences to enhance the strength around the knee, and to prevent future injuries to the knee. Bracing may also be required if the stability of the ligament is insufficient.

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